Tipping device for work holder

ABSTRACT

A workpiece processing machine having a work holder mounted to pass curved bowl portions of workpieces in and out between a pair of processing rolls is provided with a device for tipping the work holder each time the workpieces are removed from between the processing rolls, whereby the tip ends of the curved bowl portions are forced into positive engagement with one of the rolls to insure uniform processing of the surface of the curved bowl portions.

O Umted States Patent .1191 1111 3,745,714 Weatherell July 17, 1973 [54] TIPPING DEVICE FOR WORK HOLDER 3,127,707 4/1964 Burt 5l/83 R Inventor: James w. weathere", C Y 3,127,708 4/l96 4 Burt 5l/84 R Assigneet Clair Co. Inc, Olean, Primary Examiney-Donald [22] Filed: Oct 14 1971 Assistant Examiner-Howard Goldberg [211 A l N 189 246 Attorney-John B. Bean, Edwln T. Bean et al.

- PP v [57] ABSTRACT '5 5 5 3 A workpiece processing machine having a work holder [58] Field of Search 51 /83 R, 84 R, 85 R, mmmed Pass 51,86 R 234 and out between a pair of processing rolls is provided with a device for tipping the work holder each time the workpieces are removed from between the processing [56] References cued rolls, whereby the tip ends of the curved bowl portions UNITED STATES PATENTS are forced into positive engagement with one of the 2,852,085 9/1952 Butrt 51/83 R rolls to insure uniform processing of the surface of the 2, 5,5 1 10 1937 Jo nson.... 5l/84 R r d bowl 2,188,223 H1940 Johnson 5l/83 R cu ve pot H1949 10 Claims, 5 Drawing Figures Johnson et al. 51/84 R PATENTEO JUL 1 7 I973 sammrs INVENTOR. I

.mmss w. wean-wee PATENTEBJUHYIQB 5345.714

SHEEI 2 BF 3 INVENTOR. JOME .S 14 Wt'AT/fEEELL A TTORNEYS PATENTEDJUHYIBYS 3.145.714 sum 3 BF 5 INVENTOR. JAMES W. WEHTHERELL AT TORNE Y5 TIPPING DEVICE FOR WORK HOLDER BACKGROUND OF THE INVENTION Machines similar to those disclosed in U.S. Pat. Nos. 2,458,708 and 2,612,005 have come into wide commercial use in the polishing and glazing of tableware, such as for instance the curved bowl portions of spoons and forks.

Machines of this type generally include a pair of parallel rolls arranged for line surface contact; a pair of brackets joumaled for pivotal movements about an axis arranged parallel to the axes of the rolls; a work holder for removably clamping handle portions of a plurality of spoons or forks to be polished and a fluid operated cylinder for producing pivotal movements of the brackets towards and away from the rolls. The work holder is supported adjacent opposite ends thereof by the brackets for free pivotal movement about an axis arranged in a spaced parallel relationship to the bracket pivot axis. As a result, upon pivotal movements of the brackets, the work holder pivot axis is forced to move along an arc and the curved bowl portions of the spoons or forks are caused to pass in and out between the rolls to provide progressive polishing or glazing of the curved bowl portions from the tip ends to the heel ends thereof. Normally, the basic polishing operation, as thus far described, requires about 45 seconds.

However, it has been found that the apparatus does not provide for uniform polishing of the curved bowl, that is the tip portion is normally not polished to the same extent as the remaining surface portions of the bowl. As a result, it has become common in the industry for the operator to manually tip the work holder before removing it from the brackets in order to positively force the tip ends into engagement with the lowermost roll. This manual operation normally requires an additional seconds and may result in non-uniform polishing of the curved bowl, particularly if not performed by a skilled operator.

SUMMARY OF THE INVENTION The present invention relates to improvements in tableware polishing and glazing machines of the general type disclosed by U.S. Pat. Nos. 2,458,708 and 2,612,005. More particularly, the present invention is directed towards an improvement whereby a work holder is automatically tipped periodically throughout the basic polishing operation to provide for uniform polishing of the surface of the curved bowl portion of a workpiece.

In one embodiment of the present invention, relatively rigid cam arms are driven by the bracket pivoting gear shaft for movement into engagement with rollers carried by the work holder, such that the tip ends of the workpieces are momentarily driven downwardly into positive engagement with the lower processing roll each time the tip ends are withdrawn from between the processing rolls.

In a modified form of the present invention, the cam arms are arranged to yieldably engage the work holder rollers, such that the tip ends are biased into progressive, relatively prolonged engagement with the lower processing roll as the tip ends are withdrawn from between the processing rolls. Spring variations permit adjustments of contact pressure between the tip ends and the lower roll as required by the thickness and/or composition of the workpiece surface being finished.

By means of the present invention the overall required processing time is reduced by about 25 percent and the need for manual manipulation of the work holder and possible polishing non-uniformities occasioned thereby is negated.

DRAWINGS The nature and mode of the present invention will now be more fully described in the following detailed description taken with the accompanying drawings wherein:

FIG. I is a front elevational view of a polishing or glazing machine incorporating the improvement of the present invention;

FIG. 2 is a fragmentary end view with portions removed or shown in phantom line for purposes of clary;

FIG. 3 is an enlarged fragmentary sectional view taken generally along line 33 in FIG. 1 and showing the method of feeding workpieces to the rolls;

FIG. 4 is a view similar to FIG. 3, but showing a modified form of the present invention; and

FIG. 5 is a sectional view taken along line 55 in FIG. 4.

DETAILED DESCRIPTION As will be apparent from viewing the drawings, the present invention is employed in conjunction with a basic tableware polishing and glazing machine of the general type disclosed by U.S. Pat. Nos. 2,458,708 and 2,612,005. As by way of reference, the basic machine is shown as including a base or frame 10, which serves to support the polishing or glazing rolls, oscillating workpiece mounting carriage, and other mechanisms for driving and/or controlling the rolls and carriage as will be hereinafter briefly described.

The rolls are indicated at 12 and 14; roll 12 normally being of relatively small diameter when compared to roll 14 and being mounted above with its axis of rotation set slightly ahead of the axis of roll 14. Rolls 12 and 14 are arranged to contact along the line of entering of the curved bowl end portions 15 of ware or workpieces l6 and serve to effect polishing or glazing of such bowl portions progressively between the tip end portions and the heel end portions thereof, 15a and 15b, respectively. The rolls may be formed of any suitable material treated in any desired manner according to the character of the work to be done.

It will be understood from viewing FIG. 2, that rolls 12 and 14 are joumaled adjacent opposite ends thereof upon rocker arms 18 and 20, which extend from opposite ends of common rocker shafts 22 and 24; shafts 22 and 24 being in turn rotatably supported by means of base mounted pedestals 26 and 28, respectively. Rocker shafts 22 and 24 are interconnected by means of meshing gears 30 and 32, such that rolls l2 and 14 are simultaneously moved towards or away from one another upon pivotal movements of an arm 34 fixed to shaft 24. Movement of arm 34 is determined by exten sion and retraction of fluid cylinder 36.

Electric motors 38 and 40 are drivingly connected to rolls l2 and 14, respectively, by belt-pulley transmissions, not shown in detail, whereby to effect rotation of rolls l2 and 14 in the direction indicated in FIG. 3 by arrows 42 and 44, respectively.

The workpiece mounting carriage of the machine generally includes a table 50, which is mounted for oscillating movement in a direction parallel to the axes of rollers 12 and 14 under the control of a fluid cylinder 52 whose construction and mode of operation is described in detail in US. Pat. No. 3,127,707. The present form of table 50 departs from that disclosed in the above mentioned patents in that it includes a pair of end standards 54 and 56 having guide slots 58 and 60, which serve to receive ratchet slide bars or rails 62 and 64 fixed to work holder operating assemblies 66 and 68, respectively. It will be understood that each of standards 54 and 56 houses gears, not shown, which are interconnected by a bridge shaft 70 and arranged to drivingly engage bars 62 and 64. Thus, upon rotation of hand wheel 72, which is drivingly connected to one of such gears, bars 62 and 64 are forced to slide within slots 58 and 60, whereby to simultaneously reciprocate assemblies 66 and 68 transversely relative to rollers 12 and 14.

Assemblies 66 and 68 mount housings 74 and 76 for pairs of upper and lower meshing gears 78 and 80, 82 and 84, respectively. Lower gears 80 and 84 are drivingly coupled by a bridge shaft 86 and upper gear 78 is drivingly connected to an oscillating fluid motor 88 carried by assembly 66. Operation of motor 88 is controlled by a quadrant 90 having a pair of trip pins 92 arranged to alternately contact motor reversing control valve 94.

As will be understood from viewing FIG. 1, a pair of axially aligned stub shafts 100 and 102, which are keyed for rotation with upper gears 78 and 82, serve to mount a pair of brackets 104 and 106, respectively for simultaneous pivotal movement about an axis arranged parallel to the axes of rolls l2 and 14. Brackets 104 and 106 are formed, as best shown in the case of bracket 106 in FIG. 2, with grooves 110 adapted to receive in slip-fitting relation therein opposite pin ends 112 of a carrying holder 114 for gripping the handle end portions 115 of workpieces 16. By this arrangement holder 114 is end supported by brackets 104 and 106 for free pivotal movement about an axis, which is arranged essentially parallel to the axes of rolls 12 and 14 and the pivot axis of brackets. Also, as will be apparent from viewing FIG. 3, this arrangement permits holder 114 to be moved by brackets 104 and 106 back and forth along a curvilinear path between pin end positions indicated as I-VII, thereby to cause the curved bowl portions of workpieces 16 to pass in surface processing engagement in and out from between rolls l2 and 14.

Workpiece holder 114 may be of any suitable construction, but is shown for purposes of illustration as including pneumatically operated, interconnected hinge devices 121-423, which serve to pivotally join upper and lower clamp bars 124 and 126; such bars co operate to releasably clamp the handle end portions 115 of a plurality of workpieces 16. Manual manipulation of holder 114 for the purpose of inserting pin ends 112 into and removing them from grooves 110 may be facilitated by the provision of handles 128.

It has been found that with machines of the type thus far described, difficulty is experienced in obtaining a uniform finish on the lower or convex surface of the bowl portions 15 adjacent tip end portions 15a. As a result, it has become common industrial practice for a machine operator at the completion of the basic 45 second processing operation to manually raise or manipulate workholder handles 128 after the workpieces are withdrawn from between the rolls such that holder 114 is tipped or pivoted about the axis of pin ends 112 relative to brackets 104 and 106 in order to force tip end portions 15a into positive engagement with lower roll 14. This manual operation, which requires on the order of about 15 seconds of additional time, may result in the improper polishing of the tip end portions if not performed by a skilled operator.

The improvement of the present invention features an arrangement by which work holder 114 is automatically tipped or pivoted about its pin ends 1 12 each time bowl portions 15 are passed out from between rolls 12 and 14, thereby to insure uniform processing of the lower surface of the bowl portion within the normal period of the basic processing operation. Otherwise stated, with conventional processing machines of the type described, predetermined free pivotal movements are imparted to workholder 114 about the axes of pin ends 112 during each cycle of automatic machine operation, such predetermined movements being occasioned by the passage of the workpiece bowl portions in and out between the rolls as the work holder pivot axis is moved back and forth along a curvilinear path of travel. After the completion of some given number of machine operation cycles the automatic portion of the processing operation is completed, but a manual operation must be subsequently performed to provide for additional finishing of the tip end portions of the workpieces in order to process same to the same degree as the remaining surface portions of the workpiece bowl portions. This is to be contrasted with a conventional processing machine equipped with a tipping device of the present invention, which is driven so as to impart pivotal movement to the work holder about its pivot axis departing from the predetermined free pivotal movements normally imparted to the work holder, each time the bowl portions are passed out from between the rolls in order to provide for uniform processing of the tip end portions within the normal period of time or number of cycles required for the automatic machine processing operation.

In the form of the present invention illustrated in FIGS. 1-3, there is provided one and preferably two cam or work holder tipping arms 130, which are fixed to extend radially from shaft 86; and a like number of cam followers 132, which are fixed to work holder 114 and arranged for engagement with the outer ends of cam arms 130.

Cam arms 130 may be in the form of metal bars suitably mounted on shaft 86, as by bolt affixed clamping blocks 134 best shown in FIG. 3. By referring to FIGS. 1 and 3, it will be seen that cam followers 132 each include a pair of L-shaped mounting brackets 136, which are affixed to the lower surface of lower holder clamp bar 126 as by bolts 137; and a roller 138, which is end supported for rotation by its associated mounting brackets. As required, one or more spacers 140 may be employed to properly space and/or rigidify each pair of mounting brackets.

During operation of a machine employing the present invention, each time brackets 104 and 106 are pivoted in a direction away from rolls l2 and 14 (upper gears 78 and 82 rotated in the direction indicated by arrow 142 in FIG. 3) to move holder 114 into its number I position whereat bowl portions 15 are fully withdrawn from between the rolls, cam arms 130 are swung upwardly into engagement with rollers 138 (lower gears 80 and 84 rotated in the direction indicated by arrow M4 in FIG. 3) thereby to substantially instantaneously force tip end portions a into engagement with roll 14. The period of engagement of cam arms 130 with rollers 138, before holder 114 reaches its number I or repeat cycle position, may be controlled by adjustments of the cam arms relative to shaft d6, but is necessarily short in order to avoid the buildup of excessive working pressures between the tip end portions and roll At the initiation of a subsequent processing cycle, cam arms 130 are pivoted by shaft 86 downwardly from engagement with rollers 138, thereby to free holder 114 for pivotal movement about pin ends 112 during movement towards turnaround" position number VII. The corresponding turnaround position of cam arms 130 are shown in phantom line in FIGS. 2 and 3.

Another form of the present invention is illustrated in FIGS. 4 and 5, wherein each previously described rigid cam arm is replaced by a two part, resiliently deformable cam arm 130' having a first part 130a fixed to shaft 86 by bolts and a modified clamping or back up block 134' and a second part 13% pivotally fixed to part 130a by a pivot pin 150. Part 1130b and clamping block 134 are counter bored at 152 and 154, respectively, to loosely retain opposite ends of a coil type compression spring 156.

As will be apparent from viewing FIG. 4, spring 156 tends to normally bias part l30b clockwise about pivot pin 150 in a direction away from clamping block 134' into a position limited by abutting engagement with a motion limiting or stop plate 158, which is fixedly mounted on part 1300.

Upon rotation of shaft 86 in the direction indicated by arrow 144 in FIG. 4, part 130a, part 13% and clamping block 134' are moved between their turnaround position shown in phantom and full line, such positions corresponding to above-mentioned position I and VII of holder 114, respectively. The arrangement is such that part 13% is moved into tipping engagement with roller 138 substantially coincident with the removal of tip end portions 15a out from between the nip of roll 12 and 14; spring 156 thereafter being progressively compressed during movement of the clamping bar 134 into its full line tumaround position. As spring 156 is compressed, it exerts a force tending to bias holder 1 14 about the axes of pin ends 1112, thereby resulting in tip end portions llSa being resiliently biased into progressive engagement with the surface of roll 14 through the are designated in FIG. 4 as a. With this construction, tip end portions 115a may be maintained in finishing contact with roll 14, during a substantially greater portion of each operational cycle and under rel atively lower, controllable working pressures, than is possible with the construction illustrated in FIG. 3. By adjustments of the orientation of cam arm 130' and clamping bar 134' relative to shaft 86 and/or by employing springs I56 having differing spring forces, the period of engagement of the tip end portions and the working pressure may be accurately controlled to achieve a desired degree of finish. As by way of example, a relatively light spring would preferably be employed when workpieces are formed with a silver plating readily subject to damage, whereas a comparatively heavy spring could be desirably employed when processing workpieces formed of stainless steel.

Another modification of the present invention would be to form the cam arm illustrated in FIGS. 1-3 of spring steel, thereby to obtain a simplified construction possessing advantages discussed with reference to the modified construction of FIGS. 4 and 5.

I claim:

l. A machine for performing a processing operation on oppositely facing surfaces of a curved bowl portion of a workpiece between tip end and heel end portions of said bowl portion, which includes a pair of essentially parallel bowl portion surface processing rolls, a work holder for supporting said workpiece adjacent an end thereof remote from said bowl portion, and drive means for supporting said work holder for free pivotal movement relative thereto about a pivot axis arranged essentially parallel to the axes of said rolls and for moving said pivot axis back and forth along a curvilinear path whereby to cause said workpiece curved bowl portion to pass in surface processing engagement in and out from between said rolls, the improvement comprising in combination:

tipping means driven by said drive means each time said work holder is moved by said drive means to pass said tip end portion out from between said rolls for driving said work holder for pivotal movement about said pivot axis thereby to force said tip end portion into surface engagement with one of said rolls.

2. A machine according to claim ll, wherein said tip ping means includes cam means driven by said drive means and cam follower means fixed to said work holder, said earn means and said cam follower means being driven into engagement each time said work holder is moved to pass saidtip end portion out from between said rolls.

3. A machine for performing a processing operation on oppositely facing surfaces of a curved bowl portion of a workpiece between tip end and heel end portions of said bowl portion, which includes a pair of essentially parallel bowl portion surface processing rolls, a work holder for supporting said workpiece adjacent an end thereof remote from said bowl portion, and drive means for supporting said work holder for free pivotal movement about a pivot axis arranged essentially parallel to the axes of said rolls and for moving said pivot axis back and forth along a curvilinear path whereby to cause said workpiece curved bowl portion to pass in surface processing engagement in and out from between said rolls, the improvement comprising in combination:

tipping means carried by said machine for resiliently biasing said work holder for pivotal movement about said pivot axis each time said tip end portion is moved out from between said rolls thereby to force said tip end portion into surface engagement with one of said rolls.

4. In a machine for performing a processing operation on oppositely facing surfaces of curved bowl portions of a plurality of workpieces between tip end and heel end portions of said bowl portions, the combina tion comprising:

a pair of essentially parallel, driven processing rolls;

a work holder for supporting a plurality of workpieces at' ends remote from said bowl portions thereof, whereby said bowl portions extend forwardly for passage between said rolls;

drive means for supporting said work holder for free pivotal movement about a pivot axis arranged essentially parallel to the axes of said rolls and for moving said work holder whereby to cause said bowl portions to pass in surface processing engagement in and out from between said rolls; and

tipping means driven by said drive means into engagement with said work holder each time said work holder is moved to pass said tip end portions out from between said rolls for driving said work holder for pivotal movement about said pivot axis thereby to force said tip end portions into surface engagement with one of said rolls.

5. The combination according to claim 4, wherein said drive means includes bracket means for pivotally supporting said work holder and pivoting means for pivoting said bracket means about an axis arranged essentially parallel to said pivot axis whereby said pivot axis is movable along a curvilinear path when said bracket means is pivoted, said pivoting means including other means coupled with said bracket means for movement in directions opposite to the directions of pivotal movement of said bracket means; and

said tipping means includes cam means carried by said other means and cam follower means carried by said work holder, said cam means and said cam follower means being driven into engagement each time said work holder is moved to pass said tip end portions out from between said rolls.

6. The combination according to claim 4, wherein said drive means includes two pairs of upper and lower meshing rotatable gears arranged one pair adjacent each end of said rolls, shaft means arranged essentially parallel to the axes of said rolls and drivingly coupling said lower gears whereby said pairs of gears are drivingly connected and upper and lower gears of each pair are rotatable in opposite directions, a pair of bracket means for supporting said work holder adjacent opposite ends thereof for pivotal movement about said pivot axis, said bracket means being fixed one to each of said upper gears for movement about an axis arranged essentially parallel to said pivot axis, and means to impart oscillating rotational movements to said gears whereby said pivot axis is movable along a curvilinear path to cause said bowl portions to pass in and out from between said rolls; and said tipping means includes at least one cam arm fixed to extend radially from said shaft means and cam arm follower means fixed to said work holder, said cam arm and said follower means being driven into engagement to effect pivoting of said work holder about said pivot axis each time said work holder is moved to pass said tip end portions out from between said rolls.

7. The combination according to claim 4, wherein said tipping means is resiliently deformable and is driven into engagement with said work holder by said drive means each time said tip end portions pass out from between said rolls thereby to resiliently bias said tip end portions into engagement with said one roll as aforesaid.

8. The combination according to claim 4, wherein said drive means includes two pairs of upper and lower meshing rotatable gears arranged one pair adjacent each end of said rolls, shaft means arranged essentially parallel to the axes of said rolls and drivingly coupling said lower gears whereby said pairs of gears are drivingly connected and upper and lower gears of each pair 6 axis, said bracket means being fixed one to each of said upper gears for movement about an axis arranged essentially parallel to said pivot axis, and means to impart oscillating rotational movements to said gears whereby said pivot axis is movable along a curvilinear path to cause said bowl portions to pass in and out from between said rolls; and said tipping means includes at least one cam arm means having a first part fixed to extend radially from said shaft means, a second work holder engaging part, means supporting said second part on said first part for pivotal movement about an axis essentially parallel to said pivot axis, and means constraining said second part for movement with said first part and said shaft means into and out of engagement with said work holder including spring means deformable upon engagement of said second part with said work holder for pivoting said work holder about said pivot axis each time said work holder is moved to pass said tip end portions out from between said rolls.

9. In a machine for performing a processing operation on opposite facing surfaces of a curved bowl portion of a workpiece between tip end and heel end portions of said bowl portion, which includes a pair of essentially parallel bowl portion surface processing rolls, a work holder for supporting said workpiece adjacent an end thereof remote from said bowl portion, and drive means for supporting said work holder for free pivotal movement about a pivot axis arranged essentially parallel to the axes of said rolls and for moving said pivot axis back and forth along a curvilinear path during each cycle of machine operation whereby to cause said workpiece curved bowl portion to pass in surface processing engagement in and out from between said rolls, the passage of said workpiece curved bowl portion in and out from between said rolls as aforesaid causing said work holder to undergo predetermined free pivotal movement relative to said drive means about said pivot axis as said pivot axis moves back and forth along said curvilinear path during each cycle of machine operation and causing upon completion of a given number of cycles non-uniform processing of said tip end portion relative to other surfaces of said bowl portion, the improvement comprising in combination:

tipping means driven by said drive means for imparting pivotal movement to said work holder about said pivot axis departing from said predetermined free pivotal movement each time said work holder is moved to pass said tip end portion out from between said rolls thereby to force said tip end portion into surface engagement with one of said rolls to provide for uniform processing of said tip end portion relative to said other surfaces of said bowl portion upon completion of said given number of cycles.

10. in a machine for performing a processing operation on oppositely facing surfaces of the curved bowl portion of a workpiece between tip end and heel end portions of said bowl portions, the combination comprising:

a pair of essentially parallel, driven processing rolls;

a work holder for supporting said workpiece at an end remote from said bowl portion thereof, whereby said bowl portion extends forwardly for passage between said rolls;

drive means, said drive means including bracket means for supporting said work holder for free piv- 9 10 otal movement about a pivot axis arranged essentipping means driven by said pivoting means for driv Paranal to the axes of said rolls and p g ing said work holder for pivotal movement about me ans for pivoting f: P said pivot axis relative to said bracket means ans arrang? i i y e to Sal pwot axls thereby to force said tip end portion into surface whereby said pivot axis lS caused to move back and 5 forth along a curvilinear path when said bracket engagement one of Sam rolls each 'd means is pivoted thereby causing said bowl portion work holder moved to P 531d P end P to pass in surface processing engagement in and out from between Said rollsout from between said rolls; and v 

1. A machine for performing a processing operation on oppositely facing surfaces of a curved bowl portion of a workpiece between tip end and heel end portions of said bowl portion, which includes a pair of essentially parallel bowl portion surface processing rolls, a work holder for supporting said workpiece adjacent an end thereof remote from said bowl portion, and drive means for supporting said work holder for free pivotal movement relative thereto about a pivot axis arranged essentially parallel to the axes of said rolls and for moving said pivot axis back and forth along a curvilinear path whereby to cause said workpiece curved bowl portion to pass in surface processing engagement in and out from between said rolls, the improvement comprising in combination: tipping means driven by said drive means each time said work holder is moved by said drive means to pass said tip end portion out from between said rolls for driving said work holder for pivotal movement about said pivot axis thereby to force said tip end portion into surface engagement with one of said rolls.
 2. A machine according to claim 1, wherein said tipping means includes cam means driven by said drive means and cam follower means fixed to said work holder, said cam means and said cam follower means being driven into engagement each time said work holder is moved to pass said tip end portion out from between said rolls.
 3. A machine for performing a processing operation on oppositely facing surfaces of a curved bowl portion of a workpiece between tip end and heel end portions of said bowl portion, which includes a pair of essentially parallel bowl portion surFace processing rolls, a work holder for supporting said workpiece adjacent an end thereof remote from said bowl portion, and drive means for supporting said work holder for free pivotal movement about a pivot axis arranged essentially parallel to the axes of said rolls and for moving said pivot axis back and forth along a curvilinear path whereby to cause said workpiece curved bowl portion to pass in surface processing engagement in and out from between said rolls, the improvement comprising in combination: tipping means carried by said machine for resiliently biasing said work holder for pivotal movement about said pivot axis each time said tip end portion is moved out from between said rolls thereby to force said tip end portion into surface engagement with one of said rolls.
 4. In a machine for performing a processing operation on oppositely facing surfaces of curved bowl portions of a plurality of workpieces between tip end and heel end portions of said bowl portions, the combination comprising: a pair of essentially parallel, driven processing rolls; a work holder for supporting a plurality of workpieces at ends remote from said bowl portions thereof, whereby said bowl portions extend forwardly for passage between said rolls; drive means for supporting said work holder for free pivotal movement about a pivot axis arranged essentially parallel to the axes of said rolls and for moving said work holder whereby to cause said bowl portions to pass in surface processing engagement in and out from between said rolls; and tipping means driven by said drive means into engagement with said work holder each time said work holder is moved to pass said tip end portions out from between said rolls for driving said work holder for pivotal movement about said pivot axis thereby to force said tip end portions into surface engagement with one of said rolls.
 5. The combination according to claim 4, wherein said drive means includes bracket means for pivotally supporting said work holder and pivoting means for pivoting said bracket means about an axis arranged essentially parallel to said pivot axis whereby said pivot axis is movable along a curvilinear path when said bracket means is pivoted, said pivoting means including other means coupled with said bracket means for movement in directions opposite to the directions of pivotal movement of said bracket means; and said tipping means includes cam means carried by said other means and cam follower means carried by said work holder, said cam means and said cam follower means being driven into engagement each time said work holder is moved to pass said tip end portions out from between said rolls.
 6. The combination according to claim 4, wherein said drive means includes two pairs of upper and lower meshing rotatable gears arranged one pair adjacent each end of said rolls, shaft means arranged essentially parallel to the axes of said rolls and drivingly coupling said lower gears whereby said pairs of gears are drivingly connected and upper and lower gears of each pair are rotatable in opposite directions, a pair of bracket means for supporting said work holder adjacent opposite ends thereof for pivotal movement about said pivot axis, said bracket means being fixed one to each of said upper gears for movement about an axis arranged essentially parallel to said pivot axis, and means to impart oscillating rotational movements to said gears whereby said pivot axis is movable along a curvilinear path to cause said bowl portions to pass in and out from between said rolls; and said tipping means includes at least one cam arm fixed to extend radially from said shaft means and cam arm follower means fixed to said work holder, said cam arm and said follower means being driven into engagement to effect pivoting of said work holder about said pivot axis each time said work holder is moved to pass said tip end portions out from between said rolls.
 7. The combination according to claim 4, wherein said tipping meanS is resiliently deformable and is driven into engagement with said work holder by said drive means each time said tip end portions pass out from between said rolls thereby to resiliently bias said tip end portions into engagement with said one roll as aforesaid.
 8. The combination according to claim 4, wherein said drive means includes two pairs of upper and lower meshing rotatable gears arranged one pair adjacent each end of said rolls, shaft means arranged essentially parallel to the axes of said rolls and drivingly coupling said lower gears whereby said pairs of gears are drivingly connected and upper and lower gears of each pair are rotatable in opposite directions, a pair of bracket means for supporting said work holder adjacent opposite ends thereof for pivotal movement about said pivot axis, said bracket means being fixed one to each of said upper gears for movement about an axis arranged essentially parallel to said pivot axis, and means to impart oscillating rotational movements to said gears whereby said pivot axis is movable along a curvilinear path to cause said bowl portions to pass in and out from between said rolls; and said tipping means includes at least one cam arm means having a first part fixed to extend radially from said shaft means, a second work holder engaging part, means supporting said second part on said first part for pivotal movement about an axis essentially parallel to said pivot axis, and means constraining said second part for movement with said first part and said shaft means into and out of engagement with said work holder including spring means deformable upon engagement of said second part with said work holder for pivoting said work holder about said pivot axis each time said work holder is moved to pass said tip end portions out from between said rolls.
 9. In a machine for performing a processing operation on opposite facing surfaces of a curved bowl portion of a workpiece between tip end and heel end portions of said bowl portion, which includes a pair of essentially parallel bowl portion surface processing rolls, a work holder for supporting said workpiece adjacent an end thereof remote from said bowl portion, and drive means for supporting said work holder for free pivotal movement about a pivot axis arranged essentially parallel to the axes of said rolls and for moving said pivot axis back and forth along a curvilinear path during each cycle of machine operation whereby to cause said workpiece curved bowl portion to pass in surface processing engagement in and out from between said rolls, the passage of said workpiece curved bowl portion in and out from between said rolls as aforesaid causing said work holder to undergo predetermined free pivotal movement relative to said drive means about said pivot axis as said pivot axis moves back and forth along said curvilinear path during each cycle of machine operation and causing upon completion of a given number of cycles non-uniform processing of said tip end portion relative to other surfaces of said bowl portion, the improvement comprising in combination: tipping means driven by said drive means for imparting pivotal movement to said work holder about said pivot axis departing from said predetermined free pivotal movement each time said work holder is moved to pass said tip end portion out from between said rolls thereby to force said tip end portion into surface engagement with one of said rolls to provide for uniform processing of said tip end portion relative to said other surfaces of said bowl portion upon completion of said given number of cycles.
 10. In a machine for performing a processing operation on oppositely facing surfaces of the curved bowl portion of a workpiece between tip end and heel end portions of said bowl portions, the combination comprising: a pair of essentially parallel, driven processing rolls; a work holder for supporting said workpiece at an end remote from said bowl portion thereof, whereby said bowl portion extends forwardly for passage bEtween said rolls; drive means, said drive means including bracket means for supporting said work holder for free pivotal movement about a pivot axis arranged essentially parallel to the axes of said rolls and pivoting means for pivoting said bracket means about an axis arranged essentially parallel to said pivot axis whereby said pivot axis is caused to move back and forth along a curvilinear path when said bracket means is pivoted thereby causing said bowl portion to pass in surface processing engagement in and out from between said rolls; and tipping means driven by said pivoting means for driving said work holder for pivotal movement about said pivot axis relative to said bracket means thereby to force said tip end portion into surface engagement with one of said rolls each time said work holder is moved to pass said tip end portion out from between said rolls. 